STUDI SKEMA PELEPASAN BEBAN MENGGUNAKAN OVERLOAD SHEDDING RELAY PADA INTERBUS TRANSFORMER 500/150 KV 500 MVA DI SUBSISTEM DELTAMAS-MANDIRANCAN

To ensure the reliability of electricity distribution, in general the loading of Interbus Transformer (IBT) is set to a maximum of 80%. However, this is not the case in the Deltamas-Mandirancan sub-system whose estimated IBT loading exceeds 80% when operating. If interference happens on one or more IBTs, other IBTs will be overloaded. Therefore, IBTs need to be equipped with a protection system with Overload Shedding (OLS) relay to overcome such problem of overloaded interferences. The OLS relay will activate when the load on IBT has reached its limit setting, by releasing the load on 150 kV system channel in stages based on the OLS scheme, as prevention from transformer total trip. In the Deltamas-Mandirancan sub-system, the OLS scheme is carried out in 2 stages with the total released load power IBT 2 of Deltamas is 205,102 MVA. OLS schemes and OCR are coordinated with the OLS setting current for IBT 1,2 Mandirancan is 1760 A and IBT 1,2 Deltamas is 1900 A, while the setting current for OCR IBT 1,2 Mandirancan is 1920 A with tms 0.09 and IBT 1,2 Deltamas are 2060 A with tms 0.087.